#-*- encoding:utf-8 -*-
string = 'abc123456'
i=3
j=5
print string
temp = string[j]
trailer = string[j+1:] if j + 1 < len(string) else ''
string = string[0:j] + string[i] + trailer
string = string[0:i] + temp + string[i+1:]
print string
abc123456
abc321456
上面的代码参考了python hashids库中的代码。